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. 2020 Mar 9;21(5):e49891. doi: 10.15252/embr.201949891

Figure 2. Intra‐SR extensions of RyR1.

Figure 2

  1. A slice through the average structure of the apo state at a position 22 Å away from the middle slice shown in Fig 1C. The intra‐SR extension is boxed on the density in red.
  2. An enlarged view of a volume‐rendered representation fitted with an atomic model (PDB: 5TB2) corresponding to the region boxed in (A). The red arrow points to a density between the bilayer leaflets; this density is at a different location from the one in Fig 1C and D.
  3. Representative SR vesicles with different distributions of inner SR density: segregated, evenly distributed, empty and empty with filaments. RyR1 particles are circled in red, and areas circled in yellow indicate accumulation of density inside the SR.
  4. The fractions of vesicles that fall into each density category for each RyR1 sample (EDTA: n = 64; 1 mM Ca2+: n = 32; 5 mM Ca2+: n = 21, technical replicates). Blue corresponds to the fraction of SR lumen vesicles showing evenly distributed density, orange to segregated density and grey to empty vesicles.
  5. Structures of RyR1 determined in the presence of increasing Ca2+ concentration (1 and 5 mM), all with intra‐SR extensions. Scale bars: 10 nm in (A) and (E), 20 nm in (C).